This invention relates to a semiconductor device of a multilevel or multilayer wiring structure. This invention also relates to a method of manufacturing the semiconductor device.
In recent years, a semiconductor integrated circuit becomes finer in structure. Such tendency is particularly remarkable in multilevel or multilayer wiring in a logic circuit. With an improvement in fineness of metal line spacing in the multilevel wiring, occurrence of crosstalk (a phenomenon that a signal on a line leaks onto an adjacent line) is inevitable between metal lines. In order to avoid occurrence of such crosstalk, it is proposed to use a low-dielectric-constant insulator layer as a line-to-line insulator layer between metal lines.
A technique of suppressing such crosstalk by using the Low-dielectric-constant insulator layer is disclosed, for example, in an article written by Shin-Puu Jeng et al and entitled "A Planarized Multilevel Interconnect Scheme With Embedded Low-Dielectric-Constant Polymers For Sub-Quarter-Micron Applications" contributed to 1994 Symposium on VLSI Technology Digest of Technical Papers, pp. 73-74. No effect is obtained unless a relative dielectric constant is equal to 3.5 or less.
In the current status, the relative dielectric constant is between 4 and 4.5 by the use of a P-SiO layer which is a SiO layer obtained by plasma chemical vapor deposition. It is therefore believed advantageous to use an organic layer having a relative dielectric constant between 1.8 and 3.5 instead of the P-SiO layer.
As one of the various known techniques using such organic layer, Japanese Unexamined Patent Publication No. 3-34558 (34558/1991) discloses a method of manufacturing a multilevel wiring structure. The method will herein be referred to as a first conventional method.
Another example of the various known techniques using the organic layer is disclosed in the above-mentioned Jeng et al article and will herein be referred to as a second conventional method.
Each of the first and the second conventional methods has various disadvantages which will later be described.